Electric traction system.



L. B. STILLWELL & F. N. WATERMAN. ELECTRIC TRACTION SYSTEM.

APPLIOATION FILED JAN.11,1905.

1,081,342. Patented Dec. 16, 1913.

3 SHEBTSSHEET 1.

7 U [in ()U OTSOUOT'S L. B. STILLWELL & F. N. WATERMAN.

ELECTRIC TRACTION SYSTEM.

APPLICATION FILED JAN.11,1905.

Patented Dec. 16, 1913.

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Mw Jr 15;; LWM LN W1 W W1 gni/twee??? @513 d tto 14411130 a 5 a L. B. STILLWELL & P. N. WATERMAN. ELECTRIC TRACTION SYSTEM. APPLICATION FILED JAN. 11.1905. I 1,0 1,342 Patented Dec. 16, 1913.

3 SHEETS-SHEET 3.

Wibwsses: ZVentonsE Specification of Letters Patent.

ELECTRIC TRACTION SYSTEM.

Patented Dec. 16,1913.-

Application filed January 11, 1905. Serial No. 240,586.

.and State of New Jersey, have invented a new and useful Improvement in Electric Traction Systems, of which the following is a specification.

Our invention relates more particularly .to the electric operation of mainline rail- Ways, and its object is to secure a higher degree of economy in operation.

To this end it consists in the combination of single phase and polypha-se equipment as herein described to utilize the advantageous features of each. When the polyphase induction motor is driven above a speed corresponding to a synchronous relation with the generator, for the numberof poles for which it is connected, or a concatenated series of induction motors are driven above a speed corresponding to synchronis'm for the combined number of poles, the motors act as generators absorbing mechanical and returning electric energy. This property enables such machines when employed as railway motors to act to retard a train and restore to the line a considerable percentage of its stored energy. Such motors, moreover, have a higher efliciency with consequent comparative freedom from overheating, can be of more substantial and less delicate construction, can be more securely protected from injury, and are of less weight and cost per horse-power than other types of motors. In addition to these advantages they have substantially uniform torque and, hence ve the maximum tractive effort for a given weight on the driving wheels, and permit of the lightest locomotive construction for a given service. Single-phase series commutating motors, onthe other hand, being essentially variable-speed motors, possess certain advantages in the acceleration of trains and invariable voltage speed control; but being variable torque motors, they do not as effectively utilize the weight on the driving wheels, and are of comparatively low efiiciency, particularly for continued low speed work, such asthe climbing of grades. The maximum economy in the operation of trains requires at all times a minimum train weight sufficient for the service. On the other hand, the minimum necessary weight of locomotives is determined by the maximum grades encountered, assuming a constant weight of train, so that on roads having heavy grades locomotives are unnecessarily heavy for service on level portions, and unnecessary power is thus consumed, while the track and bridges are deteriorated by the great weight of the locomotives. The threephase equipment will pull considerably more per ton on drivers than either steam or single-phase equipment, so that while an excessive weight is required for single-phase locomotives per given tractive effort, polyphase locomotives permit of a reduction of weight as compared with steam equipment. In order to utilize these several features and secure a system in which maximum flexibility and economy are possible, we propose to combine the two kinds of equipment for operation in a single-system. Tothis end we divide the road to be operated into sections according to gradients and character of service. For service on the level sections of the line, or for such portions of the service as may be desired, we provide singleghase locomotives or motor car trains whose riving wheel Wei hts are roportioned to the requirements 0 such sectlons, the trolley circuits of such portions being ordinarily single phase, while sections of the line having ascending or descending grades are equipped with polyphase contact conductor circuits from which the single-phase equipment will or may also be-operated, and polyphase locomotives are provided or polyphase equipment carried on the car to operate in ascendin and'furnish a means of recuperative bra ing in descending such grades.

Since the train energy" available for recuperation and restoration to the line in descending at grade. is less than that required i for ascending by twice the energy required to overcome train reslstance at the same 100' speed, a polyphase locomotivewh'ose weight and power is sutficient to supplement the locomotive used on thelevel in ascending a grade, will usually ossess a suflicient capacity and tractive e ort to control the train 105 on the descent with little or nomechan'ical braking, thus efiecting an important saving in energy and in wear and tear on the brake equipment.

Referring to the drawings, Figure 1 is a 1-10 diagram illustrating suitable arrangements and connections for carrying out our invention,'and Figs. 2, 3 and 4: are modified arrangements for the" same purpose. Fig. 5 is a diagram illustrating the connections of anautomatic rheostat device. Fig. 6 is a diagram illustrating the connections ofanother automatic rheostat device.

Similar reference figures indicate the same or corresponding parts in all the figures.

The following is a description of thestructures diagrammatically illustrated inthe drawings, which show our invention a plied in formsat present preferredby us, ut it will be understood that various modifications and drawings m'a be made without departing from the spirit of our invention and without exceeding the scope of our claims Referring to Fig. l, G typifies a threephase generating station, supplying high tension current, either directly or through step-up transformers T, to transmitting wires 1, 2 and 3. S indicates a sub-station having transformers 4 and 5 and the usual switchin and protecting devices (not shown in the gure). The transformers are so connected and proportioned, in a manner well understood in the art, as to furnish two phase current of the required tension to secondary'leads 6, 7 and .8. 13 represents in side elevation the rails of the railway tracks on a level portion of the road, and 14 similarly represents a portion on a grade. Lead 7 being the common wire of the two phase secondary system, is connected to the track, as shown, while leads 6 and 8 are connected to singlephase trolley or contact conductor sections 9 and 10 mounted in suitable relation to the track to furnish current-t0 trains moving thereon. 11 and 12 are two contact conductors corresponding to the portion of the line 14, and are connected respectively to leads 6 and 8 from the sub-station. The single-phase and polyphase sections need not, and in general will not,*be supplied from the same sub-stations, but will have separate sub-stations, as indicated in Fig. 2 in which substantially the same circuits are shown. In Fig. 1, 15 indicates a single phase locomotive on section 5), and 17 the train drawn thereby, 16, 17 and 18 a similar train with a two phase locomotive attached in addition to the single-phase locomotive, 18 being the two phase locomotive, 17 the drawn train and 16 the single-phase 'locomotive. It will, of course, be understood that the two-phase. locomotive may be at either end of the train. The single-phase locomotive 16, may take current from either contact conductor 11 or 12, while the two phase locomotive 18, receives current from both. here the single-phase equipment cons-rat of two or more motor units, current collectors may be applied to each of the contact COIltliitilUfS it and .2, thus more evenly dividing the load on the generator and rendering substantially uniform the torque of the single-phase equipment, since the pulsa tions of torque of motor units supplied from conductor 11 will occur in quadrature with those of units supplied from conductor 12.

\Ve have indicated such an arrangement in Fig. 3, where 19 and 20 are motor cars of a multiple unit control train and 21 is a polyphase locomotive. Itis, of course, obvious that a single-phase locomotive provided with two or more sets of motor units 'may, by the provision of two current col' lectors, be similarly operated. In ascending a grade the polyphase locomotive and the single-phase motor car or locomotive are both in operation, the speed of the polyphase locomotive being made that at which it is desired to make the ascent. In descending the sin le-phase locomotive may be disconnected rom the circuit, and by an acceleration of the train of a few per cent. the polyphase locomotive will return energy to the line, and hold the train at a uniform speed.

Instead of employing separate singlephase and-poly hase motors or locomotives, itis evident t at a motor possessing the and polyphase currents would be the substantial equivalent of the motors described withinthe spirit of our invention in its broader aspects and within the scope of our claims. employment of a supplemental locomotive on grades supplied with polyphase contact conductors, the same motor being at one time operated with single-phase and at another time with polyphase currents.

The polyphase locomotives are preferably arranged for cascade or concatenated control, whereby two or more economical speeds are obtained for ascending or descending, and the single-phase locomotives or motor cars can advantageously be provided with inductive control apparatus for greater ease in attaining any desired division of load, all as well understood in the art; but neither of these features is essential.

For certain classes of service, particularly express service, where frequent accelerations or reduction of speed are not demanded, polyphase operation has many advantages over single-phase, particularly in the high efliciency of the motors and in the maintenance of speed independently of the load This would render unnecessary the and of the line voltage. For the purpose of sion and railway line with single phase cont-act conductor sections connected respecti'velyto the several bases of the threehase system, and po 'yph'a'se' sections con- 5 nested for the operation of three phase locomotives. In this instance a neutral wire is .prefer'abiy employed for better regulation and division load (in the three-fhase generating a paratus and circuits. n this figure G represents a generating station and 1, 2 and 3 the transmission lines, N being the chiral wire. Contact; conductor sections 0, 51, and 52 are s'u'p' lied from transformrs 1 2', 3' connected res ectively between 5 conductors i, 2 and a, and the neutral wire (In the polyp hase section conductors 53 and 54 are connected. to two of the terminals, while the track 14 is connected to the third terminal of a bank of transformers 55, shown in delta-"connection, though they ma equally well be in Y=eoi neetion Itis not, or course necessary that the poiyphas'e section's should in this case also be connected for three-phase currents, as two pha ms in quadrature is equally wen be used. I The neutral wire N may or may out be grounded by connect-ion to the track as shown at N in Fig. 4:. as shown the track is connected to the neutral wire and to the so Curres 'iondin'gsecondary oints on single phase sections 50, 51 and '52, While on the pol-yphase section it is connected to one leg of the three phase circuits; This is shown for the urpose ofgen'e'rill illustration, and when em toyed in notice the transformers must be nsulated or the additional strains thus pr'fluced.

The iihmngement of the several singlephase sections illustrated in the figure is' 40 shown for single tra k only, and is to be understood as purely diagrammatic; Iii '1 double track service, each track may be regarded as part of a different section, as the term is employed in this specification and in our claims and act-inn construction the several: single-phase circuits will be so arranged onthe individual phasesasto disr tribute the load as nearly as possible uni-- formly with the average division of service '50 required by the timetable. Since, however such division of load can never. be perfect, Hthe distribution of load on the generator, will, in eneral, be unsymmetrical. The olypimse sections, however, will load the generates symmetrically when absorbin pswer and when returnm power willtend to deliver it symmetricafiy to the several circuits.

In the event of a snmlir demandfor en'- ergy on one phase than is returned by the 1 moving train, such surplus energy would be returned to the generator, thus driving it from one or more phases as a motor and delivering energy over the remaining phases. as In such cases a polyphase synchronous motor "In this figure G latoron the system, and thus combine equaliiihg a'ndregulating features in a manner particularly useful in the system constitut- 111 t-he'subject of this invention.

he restoration of energy in the descent of grades demands that there be ainininmm consumption of energy by the rest of the systern equal to that given out at any time by a train or trains descending, as otherwise a dangerous condition may be produced, since the whole system must speed up until its losses equal the energy bein' returned. In order to prevent such a resu t we provide a suitable regulating device which may consist ofii variable resistance rheostat, autoinat-ically "cut into the circuit whenever the energy returned to the line by the moving trains exceeds the losses of the system atthe mains-1 frequency, such rheost'at, or other power con'sumin device, being under the joint control. of t line currents on the generator-side and train-side of its point of at- '9 tachinsiitto the system. Fig. 5 is a diagramm'atical illustration of such anarrangement.

typifies a normal generatiii-g source and M t 'e train returning energy to the. transmission lines 1, 2, 3. 29 represenfs, dia raminatically,-a rheostat (with or without t e interposition of transforming apparatus Tyeonnected to wires 1 and 2,

and to wire 3 between two series transformas 30 31, through a threeole switch 32, normally held open' by a spring 33. This switch is under the control of a suitable reverse current switch, such as the compound magnet 34, one coil of which is connected to the secondary of the transformer 30,'whi1e the other is connected in shunt to the circuit 2, 3 either directly or through a transformer 35. The two coils of magnet 34 are so connect'ed that under normal conditions their eiiects are in opposition and produce no actusting effect upon the switch 32. Since in such a system the current is always laggin I and the power factor less than unity, and since the electro-Inotive forces in the secondarics of transformers 30, 35 are not in phase, suitable adjustable resistance and reactance devices 36 and 37 may be inserted to render the currents in the coils substantiallly in phase for the average power factor of t e system. In the event of an excess of energy returned to the line from the train motor M, the current through transformers 30, 31 will be reversed thus energizing compound magnet 34 and actuating the switch 32, therebyconnectmgthe rheostat 29 to the as shown.

circuit and providing a means of absorbing the returned energy.

The resistance that the rheostat should have at any moment will depend upon the energ to be absorbed, and it is desirable, there ore, that such rheostat should be automatically adjustable to the load on the system. Various means of accomplishing this result are possible, that indicated in the drawing being the employment of a li uid rheostat, the level of the liquid in whic is automatically raised and lowered by air pressure admitted to an annular chamber 40 above the liquid, through a pipe 41, from a source of air pressure 42. Air valves 43 and 44 are provided in the pipe 41, the valve 43 being normally open to the atmosphere and venting the rheostat, and valve44 normally closing the air supply pipe. The valve 44 is actuated by the compound magnet 34, while valve 43 is actuated by a similar magnet 38, Upon the closing of the switch 32 the valve 43 is closed to the atmosphere and both valves are opened'to the source of air pressure, admitting air under pressure to the rheostat, and causing a progressive rise of the level of the liquid thereinuntil such time as the losses of the system are equal to the energy returned by the moving train. When this point is reached, current will fiow from the generator G into the rheostat 29, thus reversing the direction of flow throughthe transformer 31 and actuating the magnet 38. This closes the valve 43, and opensa vent permitting the slow escape of air from the rheostat. When the normal direction of flow is restored, the switch 32 is opened and the air valve 44 is closed. It will, of course, be understood that any suitable form of reverse current switch and magnet mechanism may be employed in place of i that here described.

employed, thus simplifying the rheostat.

' Tnstead of the apparatus of Fig. 5, any Well known form of over-speed overning device may be employed, driven directly from the generators, or from a synchronous motor operated on circuits 1, 2, 3 and acting to connect the rheostat and to vary the resistance thereof to keep the speed below a predetermined limit. Fig. 6 shows diagrammatically such an arrangement. In this figure 60 is a governor of usual type which may or may not also be the engine governor it being only necessary that it be driven b and have adefinite speed relation to tie system. An arm 61 pivoted at 62 makes contact at 63 when a speed above normal is-reached completing circuit of battery 64 through an electromagnet switchclosing-device 65, shown for convenience an electromagnet, thus closing switch 32 and connecting the line wires 1, 2, 3 to rheostat 66. A resistance varying contact device 67 is arranged to be moved to vary the resistance by an electromagnetic device, shown torpurposes of illustration as an electromagnet 68, which is normally controlled by a spring 69 to keep the contact device 67 in the position of maximum resistance. The device 68.is controlled by a reverse current relay 70 which acts to close the circuit of magnet 68 at contact point 71 upon a reversal of the flow of energy, being normally out of contact. When the contact 71 .is closed the magnet 68 is energized and moves contact device 67 to reduce the resistance. A device, as the dash-pot 72, may be employed which permits the contact device 67 to be quickly moved to reduce resistance but I to move slowly to increase it. A rotary converter or motor generator feeding storage batteries may also be employed and may be adjusted to absorb energy when the speed of the system tends to increase and to deliver energy to it when the speed tends to decrease. The ,connections for such an arrangement are or may be similar to those employed in a direct-current system with the exception that the direct-current side of the rotary converter is connected to the batteries only. Such connections being familiar to all those skilledi the art we do not specifi of elements mentionedis intended to indicate that' the omitted elements or features are not essential to the invention thereincovered.

Having thus described ourinvention in forms at present preferred, what we claim 1s:

1. A power transmission system having a polyphase generating source, in combination with translating means at times consuming,

and at times supplying energy, and means for absorbing energy applied to the system in excess of the demand therefor.

2. In an alternating current power transmission system, the combination of a source of polyphase current, a, motor operating when driving a load to draw energy from the system and- When driven by the load to return energy to it, and means for absorbing such returned energy in excess of the requirements of the system;-

3. In an electric railway system the combination of a source of polyphase" currents,

V the system and when driven by the load to energy in return energyto it, and automatic means for absorbing such returned energy in excess of the requirements of the system.

5. In an alternating current power transmission system, the combination of a source .of polyphase current, translating devices operable therefrom, a'motor operating when driving a load to draw energy from the system and when driven by the load to return energy to it, and means automatically controlled by the flow of current in the system for absorbing such returned energy in excess of the requirements of the system.

6. In an alternating current power transmission system, the combination of a source of polyphase current, translating devices operable therefrom, a motor operating when drivinga load to draw energy from the system and when driven by the load to return energy to it and a rheostat for absorbing suc'h, returned energy in excess of the requirements of the system.

7. In an alternating current power transmission system, the combination of a source of polyphase current, translating devices operable therefrom, a motor operating when driving a load to draw energy from the system and when driven by the load to return energy to it, and an automatically controlled rheostat to absorbsuch returned energy in excess of the requirements of the system.

8. In an alternating current power transmission systemthe combination of a source of polyphase current, a motor operating when driving a load to draw energy from the system and when driven by the load to return energy to it and a rheostat automatically cut into circuit by the return of current to the generator for absorbing such returned system.

9. Inan alternatingpower transmission system for railways, the combination of a source of polyphasecurrents, transmission circuits feeding successive sections of a railway track wlth current from individual phases and'polyphase currents to other sections, a railway vehicle having a motorsucexcess of the requirements 'of the sections of track supplied by polyphase currents and absorbing polyphase energy when" propelling the vehicle and delivering energy to the line when the vehicle speed exceeds that corresponding to the frequency of thealternating current supply, and a regulating means connected to said circuits and operat= ing to balance and regulate said system. A

10. In an alternating current power transmission system the combination of a motor operating when driving a load to absorb energy and when driven by the load to restore energy, a generator, a rheostat connected between the generator and working circuits, automatic switching devices operating to connect said rheostat to the circuit on the return of energy to the generator, and an automatic controlling device for varying the resistance of said rheostat.

11. In an alternating current power transmission system, the combination of a motor operating when driving a load to absorb energy, and when driven by the load to restore energy, a generator, a 'rheos'tatconnected b tween generator and working circuits, 111 ns connected on the work circuit side of said rheostat for automatically connecting said rheostat to the circuit and means on the generator side for automatically increasing and decreasing the resistance of said rheostat.

12. In an electric railway system, a generator, a working circuit comprising means for operating portions of the system by single-phase current and portions by polyphase current, an induction motor operating when driving a load to absorb energy, and when 4 In-testimonywhereof we havesigned our names to this specification in the presence of two subscriblng witnesses.

LEWIS B. ,STILLWELL.

FRANK N. WATERMAN.

Witnesses:

W. E. BUNDLE, F. W. NEWSON. 

